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Year 2 > Physiology Consequences Of Lung Diseases > Flashcards

Physiology Consequences Of Lung Diseases Flashcards

1
Q

What is ventilation?

A

Exchange of gas between the air and the atmosphere.

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2
Q

What is perfusion?

A

Delivery of RBCs carrying oxygen to the lung tissues.

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3
Q

What is the V/Q ratio?

A

Ratio of ventilation to perfusion which should be greatest at the apex of the lung where there is higher ventilation than perfusion.

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4
Q

What are the components of the pulmonary system?

A

Respiratory drive
Ventilation
Perfusion
DIffusion

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5
Q

What is capacity?

A

Maximum spontaneous ventilation which can be maintained without respiratory muscle fatigue. This can be reduced by disease processes.

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6
Q

What are the components of lung capacity?

A

Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume

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7
Q

Which measures are associated with ventilation?

A
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8
Q

What is Td?

A

Volume of air moving in and out of the lungs in one breath.

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9
Q

What is Inspiratory reserve volume?

A

Volume of air which can be forcefully inspired above the tidal volume

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10
Q

What is expiratory reserve volume?

A

Volume of air which can be expired beyond the tidal volume.

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11
Q

What is residual volume?

A

Volume of air remaining in the lungs which can’t be expelled after maximum expiration in order to keep the alveoli inflated.

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12
Q

What is functional residual capacity?

A

Volume of air remaining in the lungs after passive expiration which includes:
Expiratory reserve volume + Residual volume

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13
Q

What is Vital capacity?

A

Maximum air which can be exhaled after air being forcibly exhaled.

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14
Q

What is the normal lung capacity of an adult?

A

600ml.

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15
Q

What is FEV1?

A

Forced expiratory volume in one second

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16
Q

What is FVC?

A

Identical to vital capacity and the maximum volume of air which an be exhaled.

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17
Q

What is minute volume?

A

Amount of air entering the lungs in one minute.
Tidal volume x respiratory rate

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18
Q

What is alveolar ventilation?

A

Exchange of gases between the alveolar and the external environment.
(Tidal volume - dead space)

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19
Q

How does inspiration occur?

A

Active process of inspiration with contraction of the muscles and passive relaxation in expiration.

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20
Q

What is airway resistance?

A

Resistance of airflow through the respiratory tract during inspiration and expiration.

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21
Q

What is compliance?

A

Ability of the lungs to stretch and expand, which relies on the production of surfactant and elastic fibres. It is altered by disease of the lungs such as fibrosis or emphysema which limits their ability to expand or reduces surfactant production. This will mean change in pressure is required for change in volume of lungs.

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22
Q

What is Fick’s law of diffusion?

A

Diffusion of a gas across an alveolar membrane is dependent on difference in gas pressure and the size of tissue so it increases with:
Gas solubility e.g CO2> O2
Increased membrane surface area
Increased pressure difference

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23
Q

What limits gas exchange between blood and tissue?

A

Blood capillary transit time
Time available for blood-tissue gas exchange before blood leaves the tissue

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24
Q

Where is V/Q ratio greatest in the lungs?

A

Apex which has a low perfusion due to a low perfusion and pulmonary intravascular pressure as a result of gravity when standing upright. Ventilation is higher than perfusion here so V/Q ratio is high.

** Alveoli are larger here.**

25
Q

Where is V/Q ratio lowest in the lungs?

A

Base of the lungs which has a greater perfusion than ventilation rate when a person is upright, due to its close position to the heart. They have smaller alveolar and greater blood flow. The V/Q ratio is lower.

** Alveoli are smaller here**

26
Q

How do the lungs respond to alveolar hypoxia?

A

Pulmonary arteries undergo vasoconstriction to divert blood to essential areas and away from high oxygen areas. This ensures there is ventilation-perfusion matching so even the highly oxygenate dblood leaving the lungs undergoes ventilation.

27
Q

What is a peak flow meter?

A

Measures flow rates that are dependent on the radius of the vessel. These are typically measurements of FEV1 and FVC for asthma patients.

28
Q

What is spirometers used for?

A

Testing lung function

29
Q

How can gas exchange be measured?

A

Patient inspires carbon monoxide- measure the concentration changes following this which reflects absorption and thickness of alveolar membrane.

30
Q

How can perfusion be measured?

A

Assess blood vessels via:
CT pulmonary angiogram
Echocardiogram for intravascular shunt

31
Q

How is the respiratory system examined?

A

Respiratory rate
Central cyanosis
Accessory muscle use
Chest movements
Breath sounds

32
Q

What is pulse oximetry?

A

Indirect measure of blood oxygen in a patient using a finger scanner, with limited accuracy.

33
Q

What is a tripod posture?

A

Sign of respiratory distress where a person is hunched over with their hands on their knees, using their accessory muscles.

34
Q

What does oxygen saturation measure?

A

Measure haemoglobin bound to oxygen which should be between 95% and 100%, indicating PaO2 is 10-12 kPA.

Oxygen saturation of 90% indicates pO2 is kPA so it is severely compromised

35
Q

How are CO2 levels regulated?

A

Highly sensitive central chemoreceptors located in the medulla between the 9th and 10th cranial nerve that are responsible for the respiratory drive by inducing ventilation.

36
Q

How are O2 levels regulated?

A

Peripheral chemoreceptors in the carotid sinus and aortic arch which are less sensitive. Patients with Type 2 respiratory failure are dependent on these receptors for respiratory drive so oxygen therapy should be avoided.

37
Q

How are HCO3- levels regulated?

A

Kidneys in the buffer system.

38
Q

How can blood gases be taken?

A

Radial artery.

39
Q

What is obstructive lung disease?

A

Reduced airflow results in difficulties with expiration, trapping air in the lungs and results in patients being prone to hyperinflation and airways are prone to collapse.

40
Q

What is restrictive lung disease?

A

Loss of lung elasticity or lung compliance to the chest wall which reduces inspiration capacity. Typically occurs in pulmonary fibrosis where there are thickened, fibrotic alveolar macrophages.

41
Q

What are the features of obstructive lung fdisease?

A

They have a reduced FEV1 but FVC is normal or reduced so the FEV1/FVC ratio is low and below 0.7.

Gas trapping can occur and cause hyperinflation. There is normal diffusion and normal perfusion typically unless alveoli are affected, such as emphysema. Obstructive lung diseases can result in a state of hypoxaemia and this can cause right heart pulmonary heart failure due to cor pulmonale.

42
Q

What is cor pulmonale?

A

Enlargement/failure of the right side of the heart due to hypertension of the pulmonary artery supplying blood to the lungs. This occurs in obstructive heart failure because there is a state of hypoxaemia so vascular resistance increases via vasoconstriction of the pulmonary artery to compensate. Results in raised venous pressure and oedema.

43
Q

What are the features of restrictive lung disease?

A

Both FEV1 and FVC are reduced, which is below 0.75 but FEV1/FVC ratio is normal.

Thickness of the alveolar membrane impairs diffusion and results typically in Type 1 respiratory failure and CO2 rises in the pre-ventilatory stage. Perfusion remains normal.

44
Q

What conditions are associated with restrictive lung disease?

A

Pulmonary fibrosis
Obesity
Chest wall deformities
Neuromuscular deformities

45
Q

What conditions are associated with obstructive lung disease?

A

Asthma
COPD
Bronchieactasis

46
Q

How does pulmonary oedema affect V/Q ratio?

A

Fluid build up reduces gas exchange in the lungs, lowering ventilation and causing low V/q ratio.

47
Q

What is v/q mismatch?

A

When there is a greater ventilation or perfusion that creates a mismatch.

48
Q

What is the consequence of low ventilation in V/Q mismatch?

A

There is reduced oxygen delivery which causes a rise in pCO2 levels. This can lead to hyperventilation and hypoxia vasoconstriction, to divert blood to better ventilated areas.

49
Q

Which conditions cause low perfusion in V/Q mismatch?

A

Pulmonary embolism due to blood clot
Late stage COPD due to capillary damage
Emphysema due to reduced blood flow
Heart disease due to pulmonary artery hypertension reducing perfusion
Cardiac shunt

50
Q

Which conditions cause low ventilation in V/Q mismatch?

A

Reduced airflow with:
Pulmonary oederna
Chronic bronchitis
Asthma
Pneumonia
Aspiration

51
Q

What is ventilatory capacity?

A

Maximum ventilation that can occur spontaneously without respiratory muscle fatigue.

52
Q

What is ventilatory demand?

A

Minute ventilation required to maintain a normal pCO2.

53
Q

What is Pouiselle’s law?

A

Equation describing factors which affect blood flow:
Q = change in pressure x radius / 8 x length

This can be used to determine laminar flow.

54
Q

What is the equation for flow?

A

Flow = change in pressure / radius

55
Q

How can gas exchange be measured?

A

Method of transfer factor, where patient inspires a low concentration of carbon monoxide, and the concentration change is measured after a 10 second breath hold. It’s also known as spirometry or DLCO.

56
Q

How can perfusion be measured?

A

Echocardiogram
CT angiogram

57
Q

When is arterial puncture indicated?

A

For blood gas of below 92%, to measure arterial blood gas.

58
Q

What are the causes of restrictive lung disease?

A

Conditions which limit lung expansion such as:
Rib cage fractures
Pulmonary fibrosis due to silicosis or exposure to asbestos
Obesity
Neuromuscular disorders which affect intercostal muscles

59
Q

What is idiopathic pulmonary fibrosis?

A

Lung tissue becomes scarred and affects the intersititum and parenchyma.

Year 2 (247 decks)

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